In relative permeability measurements involving crude oil and brine, it becomes necessary to measure the volume of crude oil produced from sub-strata cores in relation to the total fluids produced. In low pressure/low temperature measurements the effluent fluid mixture from the core is collected in glassware at atmospheric pressure and the relative volumes can be calculated. The use of glassware, however, for high pressure/high temperature measurements involving volatile crude oil, is not practical since such fluids when collected would volatilize and would also change in density. No prior art technique or device is known for measuring volumes at high pressures and temperatures which result in measurements free from fluid expansion and vaporization errors.
A patentability search was conducted and the following patents were uncovered:
______________________________________ U.S. Pat. No. Inventor Issue Date ______________________________________ 3,701,006 George D. Volkel, et al 10-24-72 2,599,413 P. P. Reichertz 6-3-52 ______________________________________
The 1952 patent issued to Reichertz (U.S. Pat. No. 2,599,413) relates to a resistivity meter for analyzing drilling and composition. Reichertz utilizes a frequency of operation in the low audio range of approximately 100 cycles per second using 90 volt batteries. The Reichertz resistivity cell contemplates a mixture of a number of different fluids including brine, oil, and drilling mud to generate an overall average value of resistivity of a particular, in time, composition of the fluids in the cell.
The 1972 patent issued to Volkel, et al. (U.S. Pat. No. 3,701,006) also relates to an apparatus for measuring the electrical resistivity of flowing drilling mud. The Volkel approach offers an improvement over the Reichertz approach in that the resistivity measuring system easily retrofits into conventional drilling mud supply systems. Volkel utilizes an elongated non-conductive tubular conduit through which a flowing stream of drilling mud is directed. An electrical current is operatively provided to pass through the flowing mud. Volkel utilizes alternating current source operating in the range of about 60 to 2000 cycles per second. Again, the Volkel approach is used to measure a composite of oil, brine, drilling mud, and other particular materials mixed together.
Neither of the above patented approaches are suitable for the precise volume determinations for oil-water permeability measurement.